In a conventional flow completion system, a tubing hanger is landed in a wellhead housing, typically a tubing head, at the upper end of a well bore, and a Christmas tree is connected to the top of the wellhead housing over the tubing hanger. The tubing hanger supports at least one tubing string which extends into the well bore and defines a production bore within the tubing string. The tubing hanger itself forms at least one vertical production bore for communicating fluid between the tubing string and a corresponding production bore in the Christmas tree located above the tubing hanger. While it is common to provide for one or more valve closures in the production bore, this is usually provided in the Christmas tree above the tubing hanger, or is run into the production bore of the tubing hanger. For some applications, it is desirable to have an in-dwelling valve closure member in the tubing hanger. For instance, should one or more of the valves in the Christmas tree need replacing, it is desirable to make provision for running in of a valve or plug in the production bore or tubing hanger. As well, it may be desirable to have a removable valve or plug in place in the tubing hanger when running or retrieving the tubing hanger. However, running of a back pressure valve or plug in the tubing hanger is a complex and expensive task, particularly if the well is remotely located.
Thus, for some applications, it is desirable to have an in-dwelling valve member in the tubing hanger. To date, ball valves have not traditionally been used for this purpose. While ball valve closure members are described in the smaller annulus bore of a tubing hanger (see for example U.S. Pat. No. 6,679,330 to Compton et al.), they are not traditionally used in the production bore. A few patents describe ball valves in the production bore of a tubing hanger, but these devices are generally complex, involving complicated actuation sleeves which are hydraulically or electrically activated for operation (see for example U.S. Pat. No. 6,698,712 to Milberger et al.). There remains a need for a simple wellhead device to provide for flow control in the production bore of a tubing hanger.